2 Chronicles 25:5

Moreover Amaziah gathered Judah together, and made them captains over thousands, and captains over hundreds, according to the houses of their fathers, throughout all Judah and Benjamin: and he numbered them from twenty years old and above, and found them three hundred thousand choice men, able to go forth to war, that could handle spear and shield.

Amaziah ... made them captains ... Since all who were capable of bearing arms were liable to serve, it was quite natural, in making up the muster-roll, to class them according to their respective families, and to appoint the officers of each cords from the same quarter; so that all the soldiers who formed a regiment were brothers, relatives, friends. Thus, the Hebrew troops were closely linked together, and had strong inducements to keep steady in their ranks.

Found them three hundred thousand choice men. This was only a fourth part of Jehoshaphat's army (2 Chronicles 17:14), showing how sadly the kingdom of Judah had, in the space of 82 years, been reduced in population by foreign wars, no less than by internal corruptions. But the full amount of Amaziah's troops may not be here stated.